Home/ Questions/Q 4267490
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-21T06:54:25+00:00

I need to evaluate an xpath expression without knowing its return value in advance.

  • 0

I need to evaluate an xpath expression without knowing its return value in advance. I don’t care about the distinction between a Node and a NodeSet, but I do care about NodeSet versus a String or a number.

For example, an xpath with a sum or concat function can return a number or a string (or boolean). An xpath with a regular xml path returns a nodeset, potentially with only one node.

How can I call the XPathExpression.evaluate() function (javadoc here)? I don’t know what QName to pass to it as the second parameter. The class XPathConstants contains the closed list of constants allowed (these are Node, NodeSet, String, Number and Boolean).

Is it possible to specify an “all” or “don’t care” value and then inspect the returned object for its type?

I thought maybe to use the overloaded version of this function, which always return a String. However, I don’t see how this will work if the xpath expression is meant to return a node set.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Following Alejandro’s hint about DOM Level 3 XPath, I found out that Xalan 2.7.1 already supports it.

    I used the class XPathEvaluatorImpl of Xalan. It works great, and I can specify ANY-TYPE as the return value. The only downside is that this functionality is not exposed in the standard javax api, at least not in Java 6.

    • 0